Aluminum-containing catalysts are among the most common Lewis acid catalysts employed in Friedel-Craft reactions. Friedel-Craft reactions are reactions which fall within the broader category of electrophylic substitution reactions. There are numerous Friedel-Craft reactions which have been studied and described in the literature. For example, a survey of these reactions is set forth in Encyclopedia of Chemical Technology, Volume 11, pp. 269-300 (John Wiley & Sons, 1983). Friedel-Crafts reactions include, but are not limited to, alkylations, cycloalkylations, thioalkylations, acylations, phosphorylations, isomerizations, disproportionations, ortho substitution reactions, condensations, arylations, polymerizations, intermolecular hydride transfer reactions, and the like. In many of these processes it is necessary to separate the aluminum-containing catalyst from the reaction product. Since the reaction product is immiscible or is part of a solution which is immiscible with water or a water solution, the separation can be easily facilitated by treating the reaction mass with water. The water serves two purposes, first, it reacts with the aluminum-containing catalyst, usually a hydrolysis reaction, to form a water soluble species and secondly, it provides a solvent in which this species can be dissolved. The result is a reaction mass having two phases, an organic phase comprised of the reaction product and an aqueous phase containing the water soluble aluminum species. The two phases are then easily separated. While this scheme is widely used, it is not without serious drawbacks. The main two drawbacks are (1) the destruction of the catalyst by the water reaction so that it is deactivated and of no further catalytic use, and (2) the formation of a process waste which is costly to dispose of.
Thus, there exists a need for a technique which allows for the facile separation of an aluminum-containing Friedel-Crafts catalyst from an organic reaction product which does not entail deactivation of the catalyst. With such a technique, the separated catalyst can be recycled for further use, thus attenuating disposal costs.